The shear modulus, also known as the modulus of rigidity, is a measure of a material's ability to resist deformation when subjected to shear stress. It quantifies how much a material will deform when a force is applied parallel to its surface. The higher the shear modulus, the stiffer the material, meaning it will deform less under the same applied force. Shear modulus is an important property in fields like engineering and materials science, as it helps predict how materials will behave under various loads. It is calculated by dividing the shear stress by the shear strain, providing valuable insights for designing structures and components in applications involving metals, polymers, and composites.